The molecular clock in humans has been reversed
Kirill Stasevich, Science and Life (nkj.ru ) based on the materials of Nature.
Age leaves a variety of molecular traces in the body. For example, we know that over time, telomeres shorten in our cells – the end sections of chromosomes that do not encode any information, but which are necessary for the stability of the chromosomes themselves. With each cell division, telomeres become shorter and shorter, and by their length it is possible to understand how long the cell has already lived and how much it has left – when the telomeric sections become very short, the mechanism of cellular self-destruction is activated.
But short telomeres are not the only molecular sign of age. There are also epigenetic marks on DNA. Epigenetic labels are chemical groups that appear both on the DNA itself and on the histone proteins that package it. Such chemical modifications performed by special enzymes arise in response to various factors, external and internal, and permanently change the activity of genes.
For example, an epigenetically modified histone protein can pack a piece of DNA in such a way that the genes recorded in this piece will be inaccessible to molecular machines reading genetic information - that is, the genes will simply fall silent. The same thing can happen if epigenetic tags get on the DNA itself – usually they talk about DNA methylation, that is, about the attachment of methyl groups.
With age, the pattern of epigenetic labels on DNA changes. And this, let's say again, is not just a pattern: it affects the work of genes, and the work of genes causes age-related changes in our body. Perhaps if we turn the epigenetic clock in the opposite direction, our cells will become younger.
Researchers from the University of California at Los Angeles write in Aging Cell about how to reverse the molecular epigenetic clock. Initially, they solved the problem of how to restore an aged thymus, or thymus gland. In the thymus, T-lymphocytes born in the bone marrow mature, here they acquire specialization and learn to recognize infection and cancer cells. But after puberty, the thymus begins to gradually degrade, decreasing in size and filling with adipose tissue. It is known that it is possible to restore the thymus with the help of growth hormone. But by restoring the thymus, growth hormone increases the likelihood of diabetes. However, diabetes can be protected with the help of special drugs, metformin (one of the most famous drugs prescribed for type 2 diabetes) and the male steroid hormone dehydroepiandrosterone.
A mixture of growth hormone, metformin and dehydroepiandrosterone was tested on nine men aged 51 to 65 years. Magnetic resonance imaging showed that in seven of them, adipose tissue disappeared in the thymus, being replaced by normal thymus tissue; judging by the T-lymphocytes in the blood of the participants in the experiment, their thymus was really restored.
On the MRI images of the thymus gland of one of the volunteers, taken immediately after the start of treatment and after 9 months, the adipose tissue is outlined with a white line. Figure from the article by Fahy et al. Reversal of epigenetic aging and immunosenescent trends in human s – VM.
And finally, when their epigenetic clocks were checked in the subjects, it turned out that these clocks had retreated for some time - that is, the new pattern of methyl tags on DNA corresponded to an earlier age compared to what it was before the experiment began. Moreover, in six people, the rejuvenated epigenetic pattern persisted six months after they stopped taking the rejuvenating cocktail.
Perhaps this effect is manifested not only in the thymus gland, but also in other organs. But even if everything is limited to the thymus, this is not so little: a lot depends on our immunity, and an elderly person can generally feel younger if his immune system is rejuvenated.
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